I. Field of the Invention
The present invention relates generally to industrial ventilation fans. More particularly, the present invention relates to cylindrical, barrel fans for providing high-volume ventilation, and to a structural adaptation for moving them.
II. Description of the Prior Art
Known prior art fans are available in many different sizes, configurations, and power ratings. High volume barrel fans shaped like cylinders are well known in the art. Typical barrel fans find wide application within industrial environments for providing auxiliary ventilation. These fans are especially useful in factory areas that are not cooled with conventional air-conditioning apparatus. Barrel fans are also used widely for ventilation applications in diverse agricultural settings, especially in the poultry and dairy industries. Typical high volume barrel fans control the direction, velocity, and volume of air being moved.
High volume ventilation fans include a rigid housing that protectively encloses the fan, its blade, and the internal drive-motor. Protective guards usually shroud the housing. So-called “box fans” have a tubular housing that is “square,” i.e., in the general form of a cube or parallelepiped. So-called “barrel fans” are characterized by tubular, drum-shaped housings, in the shape of a cylinder or tube. Barrel fins may have direct-drive motor-fan combinations, or with common “tube axle” designs, the drive motor may be coupled to the propeller with a flexible drive belt. Depending upon the chosen design and configuration of a given fan, different accessory items such as screen guards, shutters, electrical controls, discharge cones, and specially-configured venturis may be deployed. Typical high capacity fans may be mounted on the ground, or secured in an elevated position upon a rigid support. The two principal fan-drive designs employed with modern high capacity fans, namely direct drive and belt-driven or tube-axle systems, have various advantages and disadvantages known in the art.
Because of their size and weight, these fans may be difficult to quickly or conveniently move to an operation position. In a factory setting, the fans may be manually moved about during a typical day between various locations. Usually they are manually moved about over smooth concrete surfaces, and some designs have handles for easing gripping tasks. Further, some large fan designs include wheels attached beneath their housing that facilitate movements. However, fork lifts or hoists are often necessary.
Typical fan wheel assemblies are rather small, compared to the dimensions of the standard barrel fan, and movements with them are sometimes difficult. For example, fins used outdoors upon golf courses need wheels with a large rolling radius. When grasped by their handles and moved over rough, uneven terrain, designs using inadequately-sized wheels are difficult to move and position without skidding. Some heavy duty fans intended for use in mines or oil fields include skids that enable them to be moved with power equipment.
Many industrial fans comprise a multi-bladed propeller that is driven at a high velocity. In response to the significant air flow generated by such fans, precession occurs, and the inappropriately-braced housing may move along the hard supporting surface in a haphazard manner. Another cause of fan vibration relates to the “V-belts” or drive belts. In such fans the blade tip speed must be less than approximately one hundred miles per hour to minimize noise. Typically the fan speed is reduced from the motor speed by a ratio of three to one. This gear reduction results from the pulleys of various sizes that are interconnected with the V-belt. Over time typical V-belts will eventually wear and deform. Thereafter the tension transmitted by the belt between the axis of rotation of the fan blade and the drive motor axis will vary in response to rotation. Unwanted vibration results, shaking the fan and adding to the noise level. Furthermore, vibration intensity generally increases over time. Many fans of this type lack an adequate stand that dependably braces it against vibration and resultant movements. Thus, once moved to the desired ventilation site, typical wheeled designs vibrate, often shifting and moving about.
Direct drive ventilation fans tend to vibrate less. The motors used in direct drive fans turn at a slower speed than motors in belt-driven systems. For example, to obtain the correct blade speed for a thirty-six inch fan the direct drive motor should turn at approximately 850 RPM. The conventional belt-driven fan, comprising a capacitor-start motor turning approximately 1750 RPM, requires two pulleys to divide the fan speed range down to approximately 500–800 RPM. Direct drive systems eliminate the complex speed reduction system and can thus reduce vibration and wear. However, the mounting systems for direct drive systems must adequately support the center of the torque moment. Often a plurality of isolation mounts located in a circular pattern help maintain shaft alignment and absorb torsional shocks. All of these adaptations raise the overall weight of the fan, and make transportation and deployment more difficult.
I have previously invented various fans with one or more of the characteristics discussed above. For example, my prior U.S. Pat. No. 5,480,282, issued Jan. 2, 1996, discloses a high-velocity cooling fan for moving large volumes of air relatively long distances. A generally U-shaped yoke, rolled from welded, nested channels, pivotally mounts the fan in a semi-permanent location upon a rigid, vertically upright post.
In prior U.S. Pat. No. 5,944,488 I have disclosed a tube axle fan assembly with deformable, convex guards that removably snap fit. The cylindrical, hollow housing is ideal for modifications according to the instant invention.
My prior U.S. Pat. No. 5,951,25, issued Sep. 14, 1999, shows a “square” fan. A parallelepiped housing protectively encloses an internal subframe securing a drive motor and fan propeller.
My U.S. Pat. No. 6,074,182, issued Jun. 13, 2000, discloses a direct drive cooling fan with a special X-shaped mounting system for securing the drive motor. The mounting chassis comprises a pair of complimentary brackets welded at opposite sides of the drive motor shell. The brackets comprise a curved, interior cradle that flushly mates with the circumferential periphery of the drive motor. The diametrically aligned cradle wings form an X-shaped profile with the motor at the center.
Finally, my U.S. Pat. No. 6,190,140, issued Feb. 20, 2001, discloses a belt-driven fan with a tension-preserving motor mounting means. In one form of the invention the housing is cylindrical.
Numerous difficulties can be encountered when moving a ventilation fan about through normal means. In response, I have developed a barrel fan whose large rolling radius makes movement easy. The design is easily moved about outdoors over grass and various obstacles without power equipment, lifts, or hoists. Once the intended location is reached, the fan stand is deployed to secure the fan in a proper operative position that resists vibration and movement during subsequent use.